Although it's a little heavy on IBM-specific acronyms and trademarks ("Agility\@Scale"), this relatively brief (20-page) whitepaper from Scott Ambler does a good job showing how agile processes are not just laissez faire "let them hack" chaos. Although this diagram makes me cringe a little (what's with the I Ching symbols for "work items"?), it puts "iteration" front and center, where it belongs.
This paper is good ammo for those who are trying to help their organizations move their software development processes beyond "classic" processes optimized for physical manufacturing.
